Collective phenomena on metallic surfaces studied with scanning tunneling microscopy and low energy electron microscopy

This thesis is devoted to the study of collective phenomena on metallic surfaces. Great part of the research was done on molecular self-assembled monolayers (SAMs), which we studied with scanning tunnelling microscopy (STM). These films are very exciting to measure at the nanoscale. We focused on the dynamics at the boundary between molecular phases, on mapping the nanoscale properties of phases, and on trying to understand the mechanisms for the SAM formation by exploring less-well studied surfaces and molecular coverage regimes. Both Au(111) and Au(001) substrates were deployed. We used the decanethiol molecule as the SAM building block. When STM was not sufficient, density functional theory (DFT) calculations were also performed. Our analysis on the phase boundary dynamics was also incorporated in a more general anisotropic triangular lattice framework.

Additionally, we wished to extend our collective phenomena framework by deploying low energy electron microscopy (LEEM) to study dynamics on the surface. However, SAMs are prone to electron-induced damage. Therefore, we alternatively looked at the Bi-modified Ni(111) surface. Bi deposition on the Ni(111) and Cu(111) surfaces has already shown to lead to a variety of dynamic processes. Therefore, the Bi/Ni system was a perfect playground for our study, with the added value that we can further expand our knowledge of its surface phase diagram. We obtained an ultrathin 3-fold symmetric Bi wetting layer and demonstrated a reproducible phase transition between an ordered and a disordered state, which occurs when heating-up the system. Upon cooling down, the original structure could be restored.